Method of manufacturing a blade with high hardness nitride layer

ABSTRACT

A blade made of a carbon steel or alloy steel is subjected to a surface nitriding process to form a high hardness nitride layer having a thickness in the range of 10 μm to 100 μm and a Vickers hardness Hv of 1000 or more, and a silver oxide layer, a copper oxide layer, or a silver oxide and copper oxide layer is formed on the high hardness nitride layer of the blade by firing. Through this processing, the blade that has a high cutting maintaining ability and an excellent sanitization ability such as antibiosis, sterilization ability, and antimold ability is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a bladehaving a high hardness nitride layer, and more particularly, relates toa method of manufacturing a high hardness blade that has high hardnessnitride layer formed on a blade processed by using a known method, andhas also a silver oxide layer, a copper oxide layer, or a silver oxideand copper oxide layer on the nitride layer.

2. Description of the Related Art

Conventionally, a blade that has a cutting edge at least at a portionthereof is extensively used for home purposes or industrial purposes forexample, a kitchen knife, a knife, scissors, a cutter, a hand ax, asickle, a shaving knife blade, a saw, an ax, a graving knife, a plane, achisel, a round cutter, a polygonal cutter. The various type andmaterial of the blade are developed and used in various fields.

In the case of a general carbon steel or alloy steel blade containingcarbon as the main ingredients, the hardness of the blade is obtained byheating or quenching. However, the upper limit value of the obtainablehardness is the HRC value of about 64, that is, the hardness of the Hvvalue of 800 or less. In result, the blade maintains the cutting abilityonly for short-term, and the sufficient cutting ability cannot beensured. If the cutting ability is reduced, the grinding operation byusing a whetstone is required. However, generally a home equipped with awhetstone is rare. Even though a study has been made for a long periodof time in order to ensure the high cutting maintaining ability, thedesirable results have not been yet obtained.

In addition, examples of forming a nitride film are as follows. There isdisclosed an austenite steel bulk material that consists of austenitenanocrystalline particles containing 0.1 to 2.0% (mass) of solidsolution type nitrogen, in which between the nanocrystalline particlesand/or in the same particles, metal or semi-metal oxide, nitride,carbide and the like are present as a grain growth inhibition substance(see Patent Document 1), or there is disclosed a nickel free highnitrogen stainless steel having excellent corrosion resistance,strength, shapability, and wear resistance, which has a chemicalcomponent composition containing (mass %) of 0<C≦0.08, 0≦Si<0.50,0≦Mn≦1.50, 15≦Cr≦30, 0≦Ni<0.05, 1≦Mo≦10, 1.00≦N≦2.00, and 0≦Ca≦0.005 andFe and impurity as the residual portion, and has the chemical componentcomposition and the clean property of the nonmetal insertion substanceso that in the contents of Cr, Mo and N, the corrosion resistance indexshown in the equation (1) containing Cr, Mo and N satisfies relationwith the area ratio of the nonmetal insertion substance in the steel inthe equations (2) and the maximum diameter of the nonmetal insertionsubstance in the steel in the equations (3) (see Patent Document 2).

[Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2004-137600]

[Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 2007-51368]

However, these references did not mention to the surface nitridetreatment in respects to the carbon steel or alloy steel blade that isextensively used in the related art.

Meanwhile, since a blade using zirconium ceramics that is mostly used inthe recent years has the hardness Hv of 1200 or more and high cuttingmaintaining ability, the blade is watched. However, since the toughnessis reduced as compared to the metal blade, the use thereof is limited.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the related art, and an object of thepresent invention is to provide a method of manufacturing a blade havinga high hardness nitride layer wherein the high hardness nitride layer isformed by performing the surface nitriding process on a carbon steel oralloy steel blade, thereby endowing the blade with a high cuttingmaintaining ability.

Another object of the present invention is to provide a method ofmanufacturing a blade having a high hardness nitride layer wherein themethod further comprises the process for forming a silver oxide layer, acopper oxide layer, or a silver oxide and copper oxide layer as a hardfilm on the surface of the blade having the high hardness nitride layerby firing, thereby endowing the blade with a sanitization ability suchas antibiosis, sterilization ability, and antimold ability.

According to a first aspect of the present invention, a method ofmanufacturing a blade having a high hardness nitride layer comprises

processing a metal steel plate so as to form a blade including a parttherein to be formed as a cutting edge;

processing the blade prepared by the above process by quenching andcuring treatment;

grinding the surface of the blade that was subjected to the quenchingand curing treatment;

forming a cutting edge in the blade that was subjected to the surfacegrinding process, by grinding;

grinding the cutting edge formed by the above process finally; and

performing surface nitriding processing on the surface of the blade thatwas subjected to the finishing process for the cutting edge thereof toform a high hardness nitride layer having a thickness of 10 μm to 100 μmand the Vickers hardness Hv of 1000 or more, wherein the surfacenitriding processing includes heating process at 600° C. or less.

According to a second aspect of the present invention, in the firstaspect, the metal steel plate comprises 10% or more chromium as astainless steel and has a HRC hardness of 35 or more by quenching andcuring treatment as heat treatment.

According to a third aspect of the present invention, in the first orsecond aspect, the method of manufacturing a blade having a highhardness nitride layer further comprises a finishing process by grindingfor forming a final cutting edge after the process for forming the highhardness nitride layer.

According to a fourth aspect of the present invention, in the thirdaspect, the method of manufacturing a blade having a high hardnessnitride layer further comprises a process for forming an electrolessnickel plating layer on the surface of the blade after the finishingprocess by grinding for forming a final cutting edge.

According to a fifth aspect of the present invention, in the third orfourth aspect, the method of manufacturing a blade having a highhardness nitride layer further comprises a process for forming a silveroxide layer, a copper oxide layer, or a silver oxide and copper oxidelayer, which is formed on the nitride layer or the electroless nickelplating layer of the blade, by dipping the blade in an aqueous solutionof inorganic copper salt compounds, an aqueous solution of inorganicsilver salt compounds, or the mixture solution of the aqueous solutions;or by applying the aqueous solution of the inorganic copper saltcompounds, the aqueous solution of inorganic silver salt compounds, orthe mixture solution of the aqueous solutions to the blade, and thenperforming heating and firing at a temperature of 450° C. or more.

The method of manufacturing a blade having the high hardness nitridelayer according to the present invention provides a blade that comprisesa high hardness nitride layer having a thickness in the range of 10 μmto 100 μm on a surface thereof, thereby endowing the blade with a highcutting maintaining ability. The high hardness nitride layer is obtainedby performing the surface nitriding process on the blade that isprepared by using carbon steel or alloy steel, wherein the carbon steelor alloy steel can be used in a manual convenience field for home orbusiness, has been manufactured in a large amount, and can be easilyobtained.

In addition, in the case of when an electroless nickel plating layer isformed on the surface of the nitride layer, the electroless nickelplating layer plays a role to prevent oxidation of the nitride layerformed on the blade, thereby endowing the blade with excellent corrosionresistance.

In addition, in the case of when a silver oxide layer, a copper oxidelayer, or a silver and copper oxide layer are formed on the nitridelayer or the electroless nickel plating layer of the blade by firing,since the blade further comprises one hard film, thereby endowing theblade with antibiosis, sterilization ability, and antimold ability, theblade has the high cutting maintaining ability and the excellentsanitization ability.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail preferred embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a sectional view of a blade of an embodiment according to amethod of manufacturing a blade having a high hardness nitride layeraccording to the present invention (1: a blade, 2: a nitride layer).

FIG. 2 is a sectional view of a blade of another embodiment according toa method of manufacturing a blade having a high hardness nitride layeraccording to the present invention (1: a blade, 2: a nitride layer, 3:an electroless nickel plating layer).

FIG. 3 is a sectional view of a blade of another embodiment according toa method of manufacturing a blade having a high hardness nitride layeraccording to the present invention (1: a blade, 2: a nitride layer, 3:an electroless nickel plating layer, 4: a silver oxide layer, a copperoxide layer, or a silver and copper oxide layer).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of a method of manufacturing a blade having ahigh hardness nitride layer according to the present invention will bedescribed in detail with reference to the accompanying drawings.

The present invention relates to a method of manufacturing a bladehaving a high hardness nitride layer, and more particularly, relates toa high hardness blade that has high hardness nitride layer formed on ablade processed by using a known method. Also, the blade may have anelectroless nickel plating layer and/or a silver oxide layer, a copperoxide layer, or a silver and copper oxide layer on the nitride layer.

A method of manufacturing a blade having a high hardness nitride layer,which is described in claim 1, comprises processing a metal steel plateso as to form a blade 1 including a part therein to be formed as acutting edge;

processing the blade 1 prepared by the above process by quenching andcuring treatment;

grinding the surface of the blade 1 that was subjected to the quenchingand curing treatment;

forming a cutting edge in the blade 1 that was subjected to the surfacegrinding process, by grinding;

grinding the cutting edge formed by the above process finally; and

performing surface nitriding processing on the surface of the blade 1that was subjected to the finishing process for the cutting edge thereofto form a high hardness nitride layer 2 having a thickness of 10 μm to100 μm and the Vickers hardness Hv of 1000 or more, wherein the surfacenitriding processing includes heating process at 600° C. or less.

In the method of manufacturing the blade having the high hardnessnitride layer which is described in claim 2, the metal steel plate ofclaim 1 comprises 10% or more chromium as stainless steel and has a HRChardness of 35 or more by quenching and curing treatment as heattreatment.

It is preferable that the metal steel plate comprises 10% or morechromium as stainless steel and has a HRC hardness of 35 or more.Examples of the metal steel plate may comprise a SUS-based alloy carbonsteel, a carbon steel-based alloy steel, a nitride steel-based alloysteel and the like.

In the case of when the metal steel plate comprises 10% or more of Cr,it is possible to form a continuous nitride diffusion layer in thesurface nitride layer by Cr at the nitriding process, and the strongfixation of the surface formation nitride layer is thereby enabled. Thestripping of the cured layer is also prevented due to an anchor effect.Thus 10% or more of Cr comprised in the metal steel plate provides thesignificant effect. In addition, due to this effect, it is possible toincrease the hardness of the nitride layer to 1000 or more.

The method of manufacturing the knife having the high hardness nitridelayer, which is described in claim 3, further comprises a finishingprocess by grinding for forming a final cutting edge after the processfor forming the high hardness nitride layer 2 in claims 1 or 2.

The method of manufacturing the blade having the high hardness nitridelayer, which is described in claim 4, further comprises a process forforming an electroless nickel plating layer 3 on the surface of theblade 1 after the finishing process by grinding for forming a finalcutting edge in claim 3.

The electroless nickel plating layer 3 plays a role to prevent oxidationof the nitride layer 2 formed on the blade 1, thereby endowing the blade1 with excellent corrosion resistance.

The method of manufacturing the blade having the high hardness nitridelayer, which is described in claim 5, further comprises a process forforming a silver oxide layer, a copper oxide layer, or a silver oxideand copper oxide layer 4 which is formed on the nitride layer 2 or theelectroless nickel plating layer 3 of the blade 1, by dipping the bladein an aqueous solution of inorganic copper salt compounds, an aqueoussolution of inorganic silver salt compounds, or the mixture solution ofthe aqueous solutions; or by applying the aqueous solution of theinorganic copper salt compounds, the aqueous solution of inorganicsilver salt compounds, or the mixture solution of the aqueous solutionsto the blade, and then performing heating and firing at a temperature of450° C. or more after the finishing process by grinding for forming afinal cutting edge in claim 3, or the process for forming an electrolessnickel plating layer on the surface of the blade in claims 4.

In the above, the aqueous solution of inorganic copper salt compoundsmay comprise, for example, copper nitrate, copper sulfate, copperchloride, and so like; and the aqueous solution of inorganic silver saltcompounds may comprise, for example, silver nitrate, silver acetate,silver bromide, and so like.

Embodiment

In the method of manufacturing the blade having the high hardnessnitride layer 2 according to the present invention, the blade 1 isprocessed by using the manufacturing means used to manufacture the bladeall over the world. That is, in the process for forming an externalshape, the metal steel plate comprises 10% or more of Cr as stainlesssteel and has the HRC hardness of 35 or more by quenching and curingtreatment as heat treatment. For example, the metal steel plate that ismade of the SUS-based alloy carbon steel, the carbon steel-based alloysteel, or the nitride steel-based alloy steel is processed by usingmeans such as press processing and the like to form a desired blade 1including a part therein to be formed as a cutting edge. The blade 1 maybe used in a kitchen knife, a knife, scissors, a cutter, a hand ax, asickle, a shaving knife blade, a saw, an ax, a graving knife, a plane, achisel, a round cutter, a polygonal cutter or the like.

Next, in the quenching and curing treatment, the heating and thequenching are performed in order to cure the blade 1 processed so as tohave the external shape. The blade 1 is thereby cured so that themaximum Vickers value Hv is 800 or less.

Subsequently, in the surface grinding process, the desired form of theblade 1 is formed by performing the surface grinding process for theblade 1 that was subjected to the quenching and curing treatment using agrinding device such as a grinder and the like. The surface grindingprocess also performs the function making the subsequent process easy.

In addition, the cutting edge forming process is that the part to beformed as a cutting edge of the blade 1 is grinded to form the sharpcutting edge using a rough grinding whetstone and the like.

In addition, the finishing process for the cutting edge is that thecutting edge is grinded to form a sharp and soft edge surface using afinish grinding whetstone and the like.

As described above, the blade 1 that is processed by using theabove-mentioned process is almost the same as those that are extensivelyused in home and various industries, but the surface of the processedblade 1 was subjected to the surface nitriding processing to form thehigh hardness nitride layer 2. The surface nitriding processing isperformed by using known means such as a plasma method, a salt bathingmethod, a sulfide gas method, an ionic method and the like.

In addition, the high hardness nitride layer 2 is a thin film that has athickness in the range of 10 μm to 100 μm, and as shown in FIG. 1, ifthe thickness A of the high hardness nitride layer 2 is 10 μm, thethickness B of the high hardness nitride layer 2 at an edge of theprocessed blade 1 is 20 μm. In connection with this, the hardness of thehigh hardness nitride layer 2 is the Vickers hardness Hv of 1000 ormore. That is, since the high hardness nitride layer 2 is formed on thesurface of the processed blade 1, the blade has the high cuttingmaintaining ability.

In addition, in a method of manufacturing a blade having a high hardnessnitride layer according to another embodiment of the present invention,an electroless nickel plating layer 3 is formed on the surface of thenitride layer 2 after the finishing process by grinding for forming afinal cutting edge.

In addition, in a method of manufacturing a blade having a high hardnessnitride layer according to another embodiment of the present invention,a silver oxide layer, a copper oxide layer, or a silver oxide and copperoxide layer 4 is formed on the surface of the nitride layer 2 or theelectroless nickel plating layer 3.

That is, the blade 1 having the nitride layer 2, or the nitride layer 2and the electroless nickel plating layer 3 is dipped in a mixturesolution of an aqueous solution of an inorganic copper salt compound andan aqueous solution of an inorganic silver salt compound, and then theblade 1 is heated and fired at a temperature of 450° C. or more.

1. A method of manufacturing a blade having a high hardness nitridelayer, the method comprising: processing a metal steel plate so as toform a blade including a part therein to be formed as a cutting edge;processing the blade prepared by the above process by quenching andcuring treatment; grinding the surface of the blade that was subjectedto the quenching and curing treatment; forming a cutting edge in theblade that was subjected to the surface grinding process, by grinding;grinding the cutting edge formed by the above process finally; andperforming surface nitriding processing on the surface of the blade thatwas subjected to the finishing process for the cutting edge thereof toform a high hardness nitride layer having a thickness of 10 μm to 100 μmand the Vickers hardness Hv of 1000 or more, wherein the surfacenitriding processing includes heating process at 600° C. or less.
 2. Themethod of manufacturing a knife having a high hardness nitride layer asset forth in claim 1, wherein the metal steel plate comprises 10% ormore chromium as a stainless steel and has a HRC hardness of 35 or moreby the quenching and curing treatment as a heat treatment.
 3. The methodof manufacturing a blade having a high hardness nitride layer as setforth in claims 1 or 2, wherein the method further comprises a finishingprocess by grinding for forming a final cutting edge after the processfor forming the high hardness nitride layer.
 4. The method ofmanufacturing a blade having a high hardness nitride layer as set forthin claims 3, wherein the method further comprises a process for formingan electroless nickel plating layer on the surface of the blade afterthe finishing process by grinding for forming a final cutting edge. 5.The method of manufacturing a blade having a high hardness nitride layeras set forth in claims 3 or 4, wherein the method further comprises aprocess for forming a silver oxide layer, a copper oxide layer, or asilver oxide and copper oxide layer which is formed on the nitride layeror the electroless nickel plating layer of the blade, by dipping theblade in an aqueous solution of inorganic copper salt compounds, anaqueous solution of inorganic silver salt compounds, or the mixturesolution of the aqueous solutions; or by applying the aqueous solutionof the inorganic copper salt compounds, the aqueous solution ofinorganic silver salt compounds, or the mixture solution of the aqueoussolutions to the blade, and then performing heating and firing at atemperature of 450° C. or more.